Study On The Mechanism Of The Cement Soil Reinforcement In The Foundation Of Protected Agirculture In Island Area

Freshwater resources shortage has been one of the important factors on restrictingnational economy and social development, and it is more seriously in the island area.Therefore, developing and utilizing seawater instead of freshwater in the architecturalengineering field is of great significance, especially for the island area. The silt soft soilfoundation is widespreaded in Zhejiang coastal area, because of its high moisture content,large porosity and lower capacity of foundation, the foundation should be reinforcedartificially before building agricultural facilities on it. Adding the cement in the mucky soilis a traditional method for soil solidification. In a typical method, using mixing cement pileto reinforce the foundation or bracing foundation pit also can solidify the soil. However, itis unsatisfactory for the effect of adding the cement in the mucky soil through theengineering practice. Frequently, phenomenon such as the insufficient strength and fractureof the mixing cement pile occur in engineering, which is adversely for the engineeringsafety and schedule. The main reason for the above problems is the low strength of thecement soil mixed with freshwater, not up to the standard of the project. When usingseawater slurry mixing to solidify the silt soil, the strength of cement soil will be greatlyimproved. But there also have problems such as easy expansion, easy to crack and so on,which can reduce the later strength of cement soil and the anti-permeability performance.Moreover, seawater can cause corrosion damage effects of steel machinery, because itcontains of massive chloride ions, sulfate and other corrosive ions.This paper aims to develop a kind of seawater mixing silt soil curing agent byexperimental method. Using seawater as mixing cement slurry water, adding ultrafinesilica powder as admixture, alkaline inorganic salt complex formula with non-toxic andlow cost as an activator to strengthen ion exchange and the secondary reaction, increasingthe crystallinity on the premise that effective control of seawater mixing clay expansion.Making the strength of cement soil to be greatly improved and slowing down the corrosionaction of seawater slurry for the metal construction equipment effectively, simultaneously.First of all, seawater mixing cement soil expansion can be effectively inhibit under thecircumstances of adding alkaline inorganic composite corrosion inhibitor formulationsNaHCO₃:Na₂HPO₄=4:1（sum of alkali is0.5%）; Secondly, experimental study on thestrength indicated that the strength of cement soil can be increased to a certain extent oncondition that adding alkaline inorganic salt NaHCO₃:Na₂HPO₄=4:1compound formula. Then with the help of the corrosion test of composite corrosion Na₂HPO₄and NaHCO₃tosteel by weight loss method, it proves that this formula can reduce the corrosive effects ofseawater cement slurry to#45steel coupons effectively. Ultimately, we study the changesof the crystalline state of seawater mixing cement soil after adding the corrosion inhibitorby SEM analysis. The results show that the inorganic compound corrosion inhibitorformulations of NaHCO₃and Na₂HPO₄can not only improve the crystalline of the cementsoils but also enhance the mechanical properties.Through the study of this subject, the problems of expansion and corrosion oncondition that using seawater instead of freshwater as cement mixing water can be solved,which is of great value in the application to the shortage of freshwater resources in islandarea. At the same time, the compound formula can improve the strength of seawater mixingcement soil, which can reduce the dosage of cement to save cost and improve the economicbenefit of the project. This finding can be applied to the projects of protected agricultureand strengthening soft foundation in soft soil foundation pit excavation and anti-seepagecurtain engineering in the coastal area.